A resin cement generally used in the dental field is categorized into a composite type and a poly(methyl methacrylate) (PMMA) type, but the present invention is limited to the composite type excellent in the physical property of the resin cement itself. In recent years, the resin cement is highly required as an adhesive for a dental prosthetic restoration composition exhibiting the aesthetic property, and the composition contains a filler consisting of an organic, inorganic and/or organic-inorganic composite material, and a polymerizable monomer or oligomer. In the restoration composition, a filling ratio of the filler is approximately not less than 50% by weight in order to achieve a high material strength. In addition, in order to polymerize and cure the resin cement even at a portion where light does not reach, a dual-cure type of the resin cement has been mainly used, which has the chemical polymerization function in addition to the photopolymerization function.
For restoring teeth which have underwent a relatively large damage due to dental caries or the like, a procedure is generally used, in which a crown, a bridge, an inlay, an onlay, etc. which is made of ceramic, composite resins or metal materials is adhered on the damaged portion with the resin cement. In such the case, a pre-treatment agent, so called a primer, is used, in order to strengthen adherability of the resin cement to a dental hard tissue. Sufficient adherability and a material strength are required for such the resin cement. Otherwise, not only the dental restorative composition may be dropped from the teeth during a long period use under severe oral environment, but also a gap may be produced at an interface between the resin cement and the teeth, and bacteria may invade therefrom and adversely effect on dental pulp.
The dental hard tissue is composed of enamel and dentin, and adhesion of the resin cement to both of them is clinically required. The primer for pre-treating a tooth surface has been conventionally used prior to application of the resin cement for enhancing adherability. Such the primer demineralizes the tooth surface to make it rough, and facilitating infiltration of the resin cement into a fine rough surface. An adhesion mechanism that, thereafter, the resin cement is cured by chemical polymerization or photopolymerization is considered.
On the other hand, as the conventional resin cement, a powder-liquid type has been used, but a resin cement which is used by mixing two pre-pasted compositions has been highly required in order to avoid a cumbersome procedure of mixing the powder and the liquid. Such the procedure of mixing the pastes reduces a mixing time and a difference between persons as compared with the procedure of mixing the powder and the liquid and, therefore, is a preferable type for clinicians. Moreover, in addition to by photopolymerization, the polymerization curing function by chemical polymerization, i.e. the dual cure polymerization curing function, is required for such the resin cement, so that it may be used for a high light-transmittable prosthetic restoration composition such as dental porcelain, in addition to a low light-transmittable prosthetic restoration composition such as a dental alloy.
However, prior to adhesion with the resin cement, each adherend of teeth, ceramic, composite resins and metal materials should be treated with an exclusive primer for each of various adherends in advance. Clinically, a simple adhesion procedure is desired, which does not require a primer treatment for such various adherends.
Japanese Patent Publication No. 2006-512466A discloses a self-adhesive resin cement which does not require the primer, that is a polymerizable composite material comprising at least one multifunctional monomer containing an acid in a concentration range of about 10-85% by weight, a non-reactive filler in a concentration range of about 1-80% by weight, a polymerization system in a concentration range of about 1.5-25% by weight, and water in a concentration range of about 0.1-25% by weight. However, since such the composition uses a single acidic monomer, sufficient adherability cannot be attained for both of inorganic component-rich enamel and organic component- and water-rich dentin.
European Patent Publication No. 1502569 A1 discloses a method for providing a two paste self-adhesive dental composition comprising a polymerizable monomer having an acidic group, a polymerizable monomer having no acidic monomer, a fine particulate filler, a reducing agent and an oxidizing agent. Specifically, it discloses that a ratio of a paste having a greater content of the polymerizable monomer having an acidic group and a paste having a smaller content of the monomer having an acidic group is greater than 1:1. When a ratio of the pastes is changed, an apparatus for feeding the paste becomes troublesome.
Japanese Patent Publication No. 2000-53518A and International Publication No. WO 02/092021A1 disclose a self-adhesive dental cement composition consisting of a liquid and a powder, but the resin cement consisting of the liquid and the powder, i.e. a powder-liquid type resin cement, is inferior in manipulability upon mixing as compared with a paste-and-paste type resin cement.
Japanese Patent Publication No. 2005-65902A discloses a dental adhesive composition comprising, as an essential adhesive component, a carboxylic acid compound having one (meth)acryloyl group and one carboxyl group which are bound to an aromatic group as a polymerizable monomer containing a particular carboxylic acid group. However, such the polymerizable monomer having a carboxylic acid group cannot impart sufficient clinically acceptable adherability for enamel.
International Patent Application No. PCT/JP2006/301845 discloses a resin cement comprising a metal salt of barbituric acid, an organic peroxide and an amine as a curing agent. However, with this resin cement, it is necessary that the teeth are pre-treated with an exclusive primer.